The present invention relates to an agricultural implement; and more particularly, it relates to an automatic reset plow. Automatic reset plows employ conventional moldboard plow bottoms, but they have the ability, upon striking an object in the ground, to be raised upward so as to clear the object, and then to re-enter the ground after passing the object.
Currently, farmers use larger plow units which may carry four to fourteen or more individual plows, and each of these units normally incorporates an automatic reset feature so that each unit may be raised and re-enter the ground independently of the others.
With the increased power of larger modern tractors, not only are the plow units able to dig at deeper depths, but the speed of plowing is a major factor to be considered in automatic reset plows. A typical speed for a plow bottom digging at a depth of 8-12 inches may be 10 lineal feet per second, which leaves very little time (about one-eighth of a second) to completely raise the plow bottom from the soil when an object is struck.
Another problem encountered in automatic reset plows is the different soil conditions, which may be caused by varying degrees of moisture in the soil as well as by soil conditions themselves. Some prior reset plows have the disadvantage that they will reset spontaneously under certain soil conditions even though an object is not struck. This problem may be further accentuated if the plow bottom is not held at a constant desired depth. For example, if the depth of plowing should increase substantially, obviously, the drag force on the plow bottom will increase substantially, and this may cause a spontaneous, undesired withdrawal of the plow.
Still another problem with certain prior construction is that after the plow bottom has been completely withdrawn, the unit does not re-enter the ground to the desired depth immediately. Considering the speed of the draft vehicle, a substantial portion of land could remain unplowed if the plow unit does not reset itself quickly.
Briefly, the present invention provides an automatic reset plow having a linkage assembly for mounting the plow bottom; and it includes a cam member and a spring unit. The spring unit urges the plow bottom into the ground, and the cam member is interconnected between the spring unit and the linkage assembly for controlling the compression of the spring unit, and thus the force urging the plow bottom into the ground. The cam member includes a seat which, in the normal plowing position, engages a roller.
The cam seat provides a threshold value of force which must be overcome by the thrust on the plow unit before the plow can be raised any appreciable amount. That is, the plow bottom will continue at plowing depth for varying conditions until it encounters sufficient obstruction to disengage the roller from the cam seat.
The cam seat includes a first portion of a cam surface which must ride over the roller before withdrawal of the plow can occur. This first portion of the cam surface is designed to cause a relatively high compression of the spring unit during initial movement of the plow tip.
Once the cam seat is disengaged from the roller, a second portion of the cam surface rides along the roller, and the shape of this second portion is such as to compress the spring unit at a lesser rate. One of the principal features of the invention is that the shape of the cam surface can be designed to account for variations in soil conditions for different localities.
The linkage assembly includes an upright rear link, an upper link and a lower link, the latter being pivotally connected between the rear link and a forward mounting position. The lower link extends rearwardly and downwardly in the normal, plowing position, whereas the upper link is approximately horizontal. When an object is encountered, the locus of the tip of the bottom is primarily rearward (allowing reaction time for the unit), and thence rearwardly and upwardly relative to its mounting, thereby enabling the plow bottom to clear the object quickly and efficiently. Further, during re-entry, the plow bottom is inclined with its tip in a downward position upon reset to facilitate rapid re-entry to the proper plowing depth. A plow shank is fixed to the rear link by an upper bolt connection and a lower bolt connection allowing for the bottom bolt to shear before serious damage would occur should an object be encountered which cannot be cleared.
Other features and advantages of the present invention will be apparent to persons skilled in the art from the following detailed description of a preferred embodiment accompanied by the attached drawing wherein identical reference numerals will refer to like parts in the various views.